User terminal, processor, and base station

ABSTRACT

A user terminal in a mobile communication system supporting D2D communication that is direct device-to-device communication comprises a controller configured to establish a D2D communication bearer used for the direct D2D communication between the user terminal and other user terminal that is a partner terminal of the D2D communication, in accordance with a parameter that characterizes a property of D2D data transmitted by the D2D communication; and a transmitter configured to transmit the D2D data corresponding to the parameter via the D2D communication bearer depending on the parameter by using a radio resource assigned in accordance with the parameter.

TECHNICAL FIELD

The present invention relates to a user terminal in a mobilecommunication system that supports D2D communication, a processorthereof, and a base station thereof.

BACKGROUND ART

In 3GPP (3rd Generation Partnership Project) which is a project aimingto standardize a mobile communication system, the introduction ofdevice-to-device (D2D) communication is discussed as a new functionafter Release 12 (see Non Patent Literature 1).

In the D2D communication, a plurality of neighboring user terminalsperform direct communication without passing through a base station.That is, a data path for the D2D communication does not pass through thebase station. On the other hand, a data path for normal communication(cellular communication) in a mobile communication system passes throughthe base station.

CITATION LIST Non Patent Literature

[NPL 1] 3GPP Technical Report “TR 22.803 V12.1.0” March 2013

SUMMARY OF INVENTION

However, there is a problem that although there is the D2D data to bepreferentially transmitted among data transmitted by D2D communication(hereinafter, referred to as D2D data), there is no mechanism in which auser terminal having D2D data to be preferentially transmittedpreferentially transmits the D2D data over other user terminals.

Therefore, the present invention provides a user terminal capable ofpreferentially transmitting D2D data to be preferentially transmitted, aprocessor thereof, and a base station thereof.

A user terminal according to one embodiment is a user terminal in amobile communication system supporting D2D communication that is directdevice-to-device communication. The user terminal comprises a controllerconfigured to establish a D2D communication bearer used for the directD2D communication between the user terminal and other user terminal thatis a partner terminal of the D2D communication, in accordance with aparameter that characterizes a property of D2D data transmitted by theD2D communication; and a transmitter configured to transmit the D2D datacorresponding to the parameter via the D2D communication bearerdepending on the parameter by using a radio resource assigned inaccordance with the parameter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram of an LTE system.

FIG. 2 is a block diagram of UE.

FIG. 3 is a block diagram of eNB.

FIG. 4 is a protocol stack diagram of a radio interface in an LTEsystem.

FIG. 5 is a configuration diagram of a radio frame used in an LTEsystem.

FIG. 6 is a diagram showing a data path in cellular communication.

FIG. 7 is a diagram showing a data path in D2D communication.

FIG. 8 is a diagram for illustrating an example of a parameter thatcharacterizes a property of D2D data.

FIG. 9 is an explanatory diagram for illustrating radio bearer used inD2D communication.

FIG. 10 is a sequence diagram showing an operation example of acontroller of the UE 100 according to an embodiment.

FIG. 11 is a sequence diagram showing an operation example of a mobilecommunication system according to the embodiment.

FIG. 12 is a sequence diagram showing an operation example of a mobilecommunication system according to a first modification of theembodiment.

FIG. 13 is a sequence diagram showing an operation example of a mobilecommunication system according to a second modification of theembodiment.

FIG. 14 is a sequence diagram showing an operation example of a mobilecommunication system according to a third modification of theembodiment.

DESCRIPTION OF EMBODIMENTS Overview of Embodiment

A user terminal according to embodiment is a user terminal in a mobilecommunication system supporting D2D communication that is directdevice-to-device communication. The user terminal comprises: acontroller configured to establish a D2D communication bearer used forthe direct D2D communication between the user terminal and other userterminal that is a partner terminal of the D2D communication, inaccordance with a parameter that characterizes a property of D2D datatransmitted by the D2D communication; and a transmitter configured totransmit the D2D data corresponding to the parameter via the D2Dcommunication bearer depending on the parameter by using a radioresource assigned in accordance with the parameter.

It is noted that the above-described “D2D communication bear”corresponds to “D2D data-use bearer” recited in the embodiment.

In the embodiment, when each of the parameters of a plurality of piecesof D2D data transmitted by the D2D communication differs from oneanother, the controller establishes a plurality of D2D communicationbearers in accordance with the parameters respectively corresponding tothe plurality of pieces of D2D data.

In the embodiment, the controller further establishes a D2D controlbearer used for controlling the D2D communication, and the controllerperforms control of transmitting and/or receiving, via the D2D controlbearer, keep-alive information for confirming that a connection betweenthe user terminal and the other user terminal is effective.

In the embodiment, the controller changes a display of a user interfaceof the user terminal when not receiving the keep-alive information for apredetermined period.

In the embodiment, the parameter is at least one of an identifier of aQoS class, a priority, a permitted delay time, and a permitted packetloss rate.

In the embodiment, the controller establishes, between a base station towhich the user terminal is connectable and the user terminal, a radiobearer used for cellular communication that is communication via thebase station, co-existing with the D2D communication bearer, and itfurther comprises a receiver configured to receive, via the radiobearer, information indicating the radio resource assigned by the basestation in accordance with the parameter.

In another embodiment, the controller determines the parameter on thebasis of at least one of past information related with the D2D data andan application used for the D2D communication.

A processor according to the embodiment is provided in a user terminalin a mobile communication system supporting D2D communication that isdirect device-to-device communication. The processor executes theprocesses of: establishing a D2D communication bearer used for thedirect D2D communication between the user terminal and other userterminal that is a partner terminal of the D2D communication, inaccordance with a parameter that characterizes a property of D2D datatransmitted by the D2D communication; and transmitting the D2D datacorresponding to the parameter via the D2D communication bearerdepending on the parameter by using a radio resource assigned inaccordance with the parameter.

A base station according to the embodiment is a base station in a mobilecommunication system supporting D2D communication that is directdevice-to-device communication. The base station comprises: a controllerconfigured to establish a radio bearer used for cellular communicationthat is communication via the base station, between the base station anda user terminal configured to perform the D2D communication; and atransmitter configured to transmit a radio resource used for the D2Dcommunication, to the user terminal via the radio bearer. The controllerassigns the radio resource to the user terminal in accordance with aparameter that characterizes a property of D2D data transmitted by theD2D communication.

With reference to the accompanying drawings, the description will beprovided for each embodiment when D2D communication is introduced to acellular mobile communication system (hereinafter, an “LTE system”)configured to comply with the 3GPP standards, below.

(LTE System)

FIG. 1 is a configuration diagram of an LTE system according to thepresent embodiment.

As shown in FIG. 1, the LTE system includes a plurality of UEs (UserEquipments) 100, E-UTRAN (Evolved Universal Terrestrial Radio AccessNetwork) 10, and EPC (Evolved Packet Core) 20. The E-UTRAN 10 and theEPC 20 configure a network.

The UE 100 is a mobile radio communication device and performs radiocommunication with a cell (serving cell) with which a connection isestablished. The UE 100 corresponds to a user terminal.

The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-Bs). TheeNB 200 corresponds to a base station. The eNB 200 manages a cell andperforms radio communication with the UE 100 that establishes aconnection with the cell.

It is noted that the “cell” is used as a term indicating a minimum unitof a radio communication area, and is also used as a term indicating afunction of performing radio communication with the UE 100.

The eNB 200 has a radio resource management (RRM) function, a routingfunction for user data, and a measurement control function for mobilitycontrol and scheduling, for example.

The EPC 20 includes MME (Mobility Management Entity)/S-GW(Serving-Gateway) 300, and OAM 400 (Operation and Maintenance). Further,the EPC 20 corresponds to a core network.

The MME is a network node that performs various mobility controls, etc.,on the UE 100, and corresponds to a control station. The S-GW is anetwork node that performs control to transfer user data, andcorresponds to a mobile switching center.

The eNB 200 is connected mutually via an X2 interface. Further, the eNB200 is connected to the MME/S-GW 300 via an S1 interface.

The OAM 400 is a server device managed by an operator and performsmaintenance and monitoring of the E-UTRAN 10.

Next, configurations of the UE 100 and the eNB 200 will be described.

FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100includes an antenna 101, a radio transceiver 110, a user interface 120,a GNSS (Global Navigation Satellite System) receiver 130, a battery 140,a memory 150, and a processor 160. The memory 150 and the processor 160configure a controller.

The UE 100 may not need to include the GNSS receiver 130. Further, thememory 150 may be integrally formed with the processor 160, and this set(that is, a chip set) may be called a processor 160′.

The antenna 101 and the radio transceiver 110 are used to transmit andreceive a radio signal. The antenna 101 includes a plurality of antennaelements. The radio transceiver 110 converts a baseband signal outputfrom the processor 160 into the radio signal, and transmits the radiosignal from the antenna 101. Further, the radio transceiver 110 convertsthe radio signal received by the antenna 101 into the baseband signal,and outputs the baseband signal to the processor 160.

The user interface 120 is an interface with a user carrying the UE 100,and includes, for example, a display, a microphone, a speaker, variousbuttons, and the like. The user interface 120 receives an operation froma user and outputs a signal indicating a content of the operation to theprocessor 160.

The GNSS receiver 130 receives a GNSS signal in order to obtain locationinformation indicating a geographical location of the UE 100, andoutputs the received signal to the processor 160.

The battery 140 accumulates power to be supplied to each block of the UE100.

The memory 150 stores a program to be executed by the processor 160 andinformation to be used for a process by the processor 160.

The processor 160 includes a baseband processor that performs modulationand demodulation, encoding and decoding, and the like on the basebandsignal, and a CPU (Central Processing Unit) that performs various typesof processes by executing the program stored in the memory 150. Theprocessor 160 may further include a codec that performs encoding anddecoding on sound and video signals. The processor 160 executes varioustypes of processes and various communication protocols described later.

In the present embodiment, the controller of the UE 100 includes a radiocontroller that controls the radio transceiver 110 and a user interfacecontroller that controls the user interface 120. The radio controllerand the user interface controller will be described in detail, later.

FIG. 3 is a block diagram of the eNB 200. As shown in FIG. 3, the eNB200 includes an antenna 201, a radio transceiver 210, a networkinterface 220, a memory 230, and a processor 240. The memory 230 and theprocessor 240 configure a controller. Further, the memory 230 may beintegrally formed with the processor 240, and this set (that is, a chipset) may be called a processor 240′.

The antenna 201 and the radio transceiver 210 are used to transmit andreceive a radio signal. The antenna 201 includes a plurality of antennaelements. The radio transceiver 210 converts a baseband signal outputfrom the processor 240 into the radio signal, and transmits the radiosignal from the antenna 201. Further, the radio transceiver 210 convertsthe radio signal received by the antenna 201 into the baseband signal,and outputs the baseband signal to the processor 240.

The network interface 220 is connected to a neighboring eNB 200 via theX2 interface and is connected to the MME/S-GW 300 via the Si interface.The network interface 220 is used in communication performed on the X2interface and communication performed on the Si interface.

The memory 230 stores a program to be executed by the processor 240 andinformation to be used for a process by the processor 240.

The processor 240 includes a baseband processor that performs modulationand demodulation, encoding and decoding, and the like on the basebandsignal, and a CPU that performs various types of processes by executingthe program stored in the memory 230. The processor 240 executes varioustypes of processes and various communication protocols described later.

FIG. 4 is a protocol stack diagram of a radio interface in the LTEsystem.

As shown in FIG. 4, the radio interface protocol is classified into alayer 1 to a layer 3 of an OSI reference model, wherein the layer 1 is aphysical (PHY) layer. The layer 2 includes an MAC (Media Access Control)layer, an RLC (Radio Link Control) layer, and a PDCP (Packet DataConvergence Protocol) layer. The layer 3 includes an RRC (Radio ResourceControl) layer.

The physical layer performs encoding and decoding, modulation anddemodulation, antenna mapping and demapping, and resource mapping anddemapping. The physical layer provides a transmission service to anupper layer by using a physical channel. Between the physical layer ofthe UE 100 and the physical layer of the eNB 200, data is transmittedvia the physical channel.

The MAC layer performs priority control of data, a retransmissionprocess by a hybrid ARQ (HARQ), and the like. Between the MAC layer ofthe UE 100 and the MAC layer of the eNB 200, data is transmitted via atransport channel. The MAC layer of the eNB 200 includes a transportformat of an uplink and a downlink (a transport block size, a modulationand coding scheme, and the like), and a MAC scheduler to decide aresource block to be assigned.

The RLC layer transmits data to an RLC layer of a reception side byusing the functions of the MAC layer and the physical layer. Between theRLC layer of the UE 100 and the RLC layer of the eNB 200, data istransmitted via a logical channel.

The PDCP layer performs header compression and decompression, andencryption and decryption.

The RRC layer is defined only in a control plane. Between the RRC layerof the UE 100 and the RRC layer of the eNB 200, a control signal (RRCmessage) for various types of settings is transmitted. The RRC layercontrols the logical channel, the transport channel, and the physicalchannel in response to establishment, re-establishment, and release of aradio bearer. When an RRC connection is established between the RRC ofthe UE 100 and the RRC of the eNB 200, the UE 100 is in a connectedstate, and when the RRC connection is not established, the UE 100 is inan idle state.

An NAS (Non-Access Stratum) layer positioned above the RRC layerperforms session management, mobility management, and the like.

FIG. 5 is a configuration diagram of a radio frame used in the LTEsystem. In the LTE system, OFDMA (Orthogonal Frequency DivisionMultiplexing Access) is employed in a downlink, and SC-FDMA (SingleCarrier Frequency Division Multiple Access) is employed in an uplink,respectively.

As shown in FIG. 5, the radio frame is configured by 10 subframesarranged in a time direction, wherein each subframe is configured by twoslots arranged in the time direction. Each subframe has a length of 1 msand each slot has a length of 0.5 ms. Each subframe includes a pluralityof resource blocks (RBs) in a frequency direction, and a plurality ofsymbols in the time direction. Each symbol is provided at a head thereofwith a guard interval called a cyclic prefix (CP). The resource blockincludes a plurality of subcarriers in the frequency direction. A radioresource unit configured by one subcarrier and one symbol is called aresource element (RE).

Among radio resources assigned to the UE 100, a frequency resource canbe specified by a resource block and a time resource can be specified bya subframe (or a slot).

In the downlink, an interval of several symbols at the head of eachsubframe is a control region mainly used as a physical downlink controlchannel (PDCCH). Furthermore, the remaining interval of each subframe isa region that can be mainly used as a physical downlink shared channel(PDSCH). Moreover, in each subframe, cell-specific reference signal(CRS) are distributed and arranged.

In the uplink, both ends in the frequency direction of each subframe arecontrol regions mainly used as a physical uplink control channel(PUCCH). Further, the center portion in the frequency direction of eachsubframe is a region that can be mainly used as a physical uplink sharedchannel (PUSCH). Moreover, in each subframe, a demodulation referencesignal (DMRS) and a sounding reference signal (SRS) are arranged.

(D2D Communication)

Next, description will be provided by comparing the D2D communicationwith the normal communication (cellular communication) in the LTEsystem.

FIG. 6 is a diagram showing a data path in the cellular communication.Here, the case is shown in which the cellular communication is performedbetween the UE 100-1 that establishes a connection with the eNB 200-1and the UE 100-2 that establishes a connection with the eNB 200-2. It isnoted that the data path indicates a transfer path of user data (userplane).

As shown in FIG. 6, the data path of the cellular communication passesthrough the core network. In particular, the data path is set to passthrough the eNB 200-1, the S-GW 300, and the eNB 200-2.

FIG. 7 is a diagram showing a data path in the D2D communication. Here,the case is shown in which the D2D communication is performed betweenthe UE 100-1 that establishes a connection with the eNB 200-1 and the UE100-2 that establishes a connection with the eNB 200-2.

For example, one UE 100 of the UE 100-1 and the UE 100-2 discovers theother UE 100 existing in the vicinity of the one UE 100, so that the D2Dcommunication starts. It is noted that in order to start the D2Dcommunication, the UE 100 has a (Discover) function of discovering theother UE 100 existing in the vicinity of the UE 100. Further, the UE 100has a (Discoverable) function of being discovered by the other UE 100.

As shown in FIG. 7, the data path of the D2D communication does not passthrough the core network. That is, direct radio communication isperformed between the UEs. As described above, when the UE 100-2 existsin the vicinity of the UE 100-1, the D2D communication is performedbetween the UE 100-1 and the UE 100-2, thereby obtaining an effect thata traffic load on the core network and a battery consumption amount ofthe UE 100 are reduced, for example.

(Parameter Characterizing Property of D2D Data)

Next, a parameter characterizing a property of D2D data that is data tobe transmitted in the D2D communication will be described with referenceto FIG. 8. FIG. 8 is a diagram for illustrating an example of aparameter that characterizes the property of the D2D data.

In the present embodiment, the D2D data is categorized in accordancewith the parameter characterizing the property of the D2D data.

For example, as shown in FIG. 8, the D2D data may be categorized byusing a QCI (QoS Class identifier) defined in the cellularcommunication.

Specifically, as the parameter that characterizes the property of theD2D data, there are an identifier of a QoS class (QCI: QoS ClassIdentifier), a resource type (Resource Type), a priority (Priority), apermitted delay time (Packet Delay Budget), and a permitted packet lossrate (Packet Error Loss Rate).

Further, the parameter of the QCI may be associated with an application(service content) used for the D2D communication. For example, in anapplication used for transmitting D2D data in Conversational Voice, theparameter of the QCI may be associated with “1”.

Further, the D2D data may be categorized by using some QCIs defined inthe cellular communication, a new QCI dedicated to D2D communication maybe defined in order to categorize the D2D data.

(D2D-Use Bearer)

Next, by using FIG. 9, a radio bearer used in the D2D communication willbe described. FIG. 9 is an explanatory diagram for illustrating a radiobearer used in D2D communication.

As shown in FIG. 9, between the UE 100-1 and the UE 100-2 that is apartner terminal of D2D communication, a radio bearer used for D2Dcommunication (hereinafter, referred to as “D2D-use bearer”) isestablished. Here, the D2D-use bearer is directly established betweenthe UE 100-1 and the UE 100-2, not a radio bearer indirectly establishedvia the eNB 200 between the UE 100-1 and the UE 100-2, for example. Thatis, the D2D-use bearer is not a radio bearer via the eNB 200.

The D2D-use bearer includes a D2D data-use bearer used for transmittingD2D data that is data in D2D communication and a D2D control-use bearerused for controlling D2D communication.

It is possible to establish the D2D-use bearer co-existing with theradio bearer used for the cellular communication that is communicationvia the eNB 200. Therefore, the UE 100 is capable of receiving, via theradio bearer, information indicating the radio resource assigned to theUE 100 in accordance with the parameter that characterizes the propertyof the D2D data.

The D2D data-use bearer is established in accordance with the parametercharacterizing the property of the D2D data.

When parameters characterizing the property of respective D2D bearers ofa plurality of pieces of D2D data differ from one another, it ispossible to establish a plurality of pieces of D2D data-use bearers inaccordance with the parameters respectively corresponding to theplurality of pieces of D2D data. For example, in order to transmit firstD2D data in which the parameter of QCI is “1” and second D2D data inwhich the parameter of QCI is “3”, a first D2D data-use bearer fortransmitting the first D2D data and a second D2D data-use bearer fortransmitting the second D2D data may be established.

The D2D control-use bearer is established when the D2D communication isstarted. In the present embodiment, the D2D control-use bearer is usedfor transmitting and/or receiving keep-alive information for confirmingthat the D2D communication connection between the UE 100-1 and the UE100-2 is effective. For example, when transmitting the D2D data via theD2D data-use bearer, the UE 100 transmits also the keep-aliveinformation via the D2D control-use bearer.

(Schematic Operation of Controller of UE 100)

Next, a schematic operation of the controller of the UE 100 according tothe embodiment will be described by using FIG. 10. FIG. 10 is a sequencediagram showing an operation example of the controller of the UE 100according to the embodiment.

The controller of the UE 100 includes a radio controller that controlsthe radio transceiver 110 and a user interface controller that controlsthe user interface 120.

As shown in FIG. 10, in step 101, the radio controller instructs theuser interface controller to display a screen displayed when the D2Dcommunication connection is effective. For example, when there is addedlimitation on the size and/or density of a text, the radio controllerinstructs returning to a default. When there is a limitation that as anumerical value C becomes larger, the size and/or density of a text ischanged, the radio controller instructs C=0.

The radio controller may notify, instead of the above-describedinstruction, the user interface controller that the keep-aliveinformation is received.

The user interface controller controls, on the basis of theabove-described instruction or notification, to display a screendisplayed when the D2D communication connection is effective.

In step 102, after a predetermined time passes since step 101, the radiocontroller determines whether or not the keep-alive information that isinformation for confirming that the D2D communication connection iseffective is received. When the keep-alive information is received, theradio controller executes a process in step 101. On the other hand, whenthe keep-alive information is not received, the radio controllerexecutes a process in step 103.

In step 103, the radio controller instructs displaying a screendisplayed when the D2D communication connection is not effective. Forexample, the radio controller instructs addition of a limitation on thesize and/or density of a text. When there is a limitation that as anumerical value C becomes larger, the size and/or density of a text ischanged, the radio controller instructs addition of a predeterminedvalue to C. For example, a limitation that the size of a text becomessmaller in accordance with the size of the numerical value C may beimposed.

The radio controller may notify, instead of the instruction in step 103,the user interface controller that the keep-alive information is notreceived.

The radio controller controls, on the basis of the instruction or thenotification in step 103, to display a screen displayed when the D2Dcommunication connection is not effective. Therefore, the controller(the radio controller and the user interface controller) changes thedisplay of the user interface of the UE 100 when not receiving thekeep-alive information for a predetermined period.

In step 104, when the numerical value C is smaller than a predeterminedvalue, the radio controller executes again the process in step 102 aftera predetermined period passes. On the other hand, when the numericalvalue C is larger than the predetermined value, the radio controllerexecutes control to end the D2D communication.

Instead of the size of the numerical value C, when a time period passingsince not receiving the keep-alive information exceeds a predeterminedvalue, the radio controller may execute similar control.

The radio controller instructs the user interface controller to displayindicating the end of the D2D communication. The user interfacecontroller controls to display a screen indicating the end of the D2Dcommunication.

(Schematic Operation of Mobile Communication System According toEmbodiment)

Next, a schematic operation of a mobile communication system accordingto the embodiment will be described by using FIG. 11. FIG. 11 is asequence diagram showing an operation example of the mobilecommunication system according to the embodiment.

As shown in FIG. 11, in step 201, the eNB 200 broadcasts broadcastinformation. Each of the UE 100-1 and the UE 100-2 receives thebroadcast information from the eNB 200.

The broadcast information is information on the parameter thatcharacterizes the property of the D2D data. Each of the UE 100-1 and theUE 100-2 determines, on the basis of the information on the parameterthat characterizes the property of the D2D data, the parameter thatcharacterizes the property of the D2D data transmitted by each of the UE100-1 and the UE 100-2.

In step 202, each of the UE 100-1 and the UE 100-2 transmits aninstruction (Indication) for requesting the D2D communication, to theeNB 200. The eNB 200 receives the instruction for requesting the D2Dcommunication from each of the UE 100-1 and the UE 100-2.

Each of the UE 100-1 and the UE 100-2 transmits, together with therequest, information indicating the determined parameter. When there area plurality of pieces of D2D data, information indicating respectiveparameters characterizing the property of each of the D2D data istransmitted.

Further, each of the UE 100-1 and the UE 100-2 may transmit, togetherwith the request, information indicating a data amount of the D2D data(data amount notification).

The eNB 200 stores the information transmitted together with therequest. It is noted that an identifier of the UE 100 from which therequest is transmitted is stored together with the request. When also apartner terminal of D2D communication of the UE 100 from which therequest is transmitted is transmitted, an identifier of the partnerterminal is also stored.

In step 203, each of the UE 100-1 and the UE 100-2 transmits ameasurement report (Measurement report) to the eNB 200. The eNB 200receives the measurement report from each of the UE 100-1 and the UE100-2.

In step 204, the eNB 200 determines whether or not to allow each of theUE 100-1 and the UE 100-2 to perform the D2D communication.

Specifically, the eNB 200 determines whether or not to allow the D2Dcommunication to be performed on the basis of at least one of a receivedsignal strength from the eNB 200 included in the measurement report, theparameter that characterizes the property of the D2D data, and the dataamount of the D2D data. When determining that the UE 100-1 and the UE100-2 are allowed to perform the D2D communication, the eNB 200 executesa process in step 205. On the other hand, when determining that the UE100-1 and the UE 100-2 are not allowed to perform the D2D communication,the eNB 200 transmits information indicating that the D2D communicationis not permitted to each of the UE 100-1 and the UE 100-2.

In step 205, the eNB 200 transmits to each of the UE 100-1 and the UE100-2 information indicating that the D2D communication is permitted. Inthe information indicating that the D2D communication is permitted,information indicating a radio resource necessary for establishing a D2Dcommunication-use bearer between the UE 100-1 and the UE 100-2 isincluded.

Further, the eNB 200 transmits, together with the information indicatingthat the D2D communication is permitted, information indicatingassignment of a D2D communication-use radio resource (bandwidthassignment).

The eNB 200 assigns the radio resource to each of the UE 100-1 and theUE 100-2, on the basis of the respective parameters characterizing theproperty of the D2D data received in step 202. Specifically, when theparameter indicates the D2D data having a high priority, the eNB 200assigns more radio resources to the UE 100 having the D2D data of theparameter. On the other hand, when the parameter indicates the D2D datahaving a low priority, the eNB 200 assigns less radio resources to theUE 100 having the D2D data of the parameter.

It is noted that on the basis not only of the parameter but also of thedata amount notification received in step 202, the eNB 200 may assignthe radio resource to each of the UE 100-1 and the UE 100-2.

In step 206, the UE 100-1 and the UE 100-2 establish the D2D-use bearerbetween the UE 100-1 and the UE 100-2. Specifically, each of the UE100-1 and the UE 100-2 establishes the D2D data-use bearer in accordancewith the transmitted parameter that characterizes the property of theD2D data. Each of the UE 100-1 and the UE 100-2 may establish the D2Dcontrol-use bearer.

Each of the UE 100-1 and the UE 100-2 uses the radio resource assignedin accordance with the D2D data-use bearer to transmit the D2D data viathe D2D data-use bearer.

It is noted that when the eNB 200 controls the D2D communication, theradio bearers are set between the eNB 200 and the UE 100-1 and betweenthe eNB 200 and the UE 100-2, the eNB 200 assigns the radio resource toeach of the UE 100-1 and the UE 100-2 in accordance with the parametertransmitted from each of the UE 100-1 and the UE 100-2, and transmitsinformation indicating the assigned radio resource, via the radiobearer, to each of the UE 100-1 and the UE 100-2. Each of the UE 100-1and the UE 100-2 uses the radio resource received from the eNB 200 toperform the D2D communication.

(Schematic Operation of Mobile Communication System According to FirstModification of Embodiment)

Next, by using FIG. 12, a schematic operation of a mobile communicationsystem according to a first modification of the embodiment will bedescribed. FIG. 12 is a sequence diagram showing an operation example ofthe mobile communication system according to the first modification ofthe embodiment. It is noted that a description will be provided whilefocusing on a portion different from the above-described embodiment, anda description of a similar portion will be omitted, where necessary.

In the above-described embodiment, the UE 100 transmits, together withthe instruction (Indication) for requesting the D2D communication, theinformation indicating the data amount of the D2D data; however, in thepresent modification, the information indicating the D2D data amount istransmitted after the D2D communication is permitted.

Step 301 in FIG. 12 corresponds to step 201 in the first embodiment.

In step 302, each of the UE 100-1 and the UE 100-2 transmits aninstruction (Indication) for requesting the D2D communication, to theeNB 200. The eNB 200 receives the instruction for requesting the D2Dcommunication from each of the UE 100-1 and the UE 100-2. Here, each ofthe UE 100-1 and the UE 100-2 does not transmit the informationindicating the D2D data amount.

Steps 303 and 304 correspond to steps 203 and 204 in the firstembodiment.

In step 305, the eNB 200 transmits to each of the UE 100-1 and the UE100-2 information indicating that the D2D communication is permitted. Inthe information indicating that the D2D communication is permitted,information indicating a radio resource necessary for establishing a D2Dcommunication-use bearer between the UE 100-1 and the UE 100-2 isincluded. Here, the eNB 200 does not transmit the information indicatingassignment of the D2D communication-use radio resource (bandwidthassignment).

In step 306, each of the UE 100-1 and the UE 100-2 transmits informationindicating a data amount of the D2D data (data amount notification) tothe eNB 200. The eNB 200 receives the data amount notification.

In step 307, the eNB 200 transmits to each of the UE 100-1 and the UE100-2 the information indicating assignment of the D2D communication-useradio resource (bandwidth assignment). Each of the UE 100-1 and the UE100-2 receives the bandwidth assignment.

It is noted that in much the same way as in the first embodiment, theeNB 200 assigns the radio resource to each of the UE 100-1 and the UE100-2, on the basis of the respective parameters characterizing theproperty of the D2D data and the data amount notification.

Step 308 corresponds to step 206 in the first embodiment.

(Schematic Operation of Mobile Communication System According to SecondModification of Embodiment)

Next, by using FIG. 13, a schematic operation of a mobile communicationsystem according to a second modification of the embodiment will bedescribed. FIG. 13 is a sequence diagram showing an operation example ofthe mobile communication system according to the second modification ofthe embodiment. It is noted that a description will be provided whilefocusing on a portion different from the above-described embodiment, anda description of a similar portion will be omitted, where necessary.

In the present modification, there is an anchor UE 100-1 representing aD2D group configured by the UE 100 that performs the D2D communication.The anchor UE 100-1 is UE that communicates with the eNB 200 as arepresentative of the D2D group.

Step 401 corresponds to step 201 in the first embodiment.

Step 402 corresponds to step 202 in the first embodiment. However, onlythe anchor UE 100-1 transmits the instruction for requesting the D2Dcommunication to the eNB 200.

The UE 100-2 transmits in advance information indicating the parameterthat characterizes the property of the D2D data transmitted by the UE100-2 and information indicating the data amount of the D2D data, to theanchor UE 100-1.

The anchor UE 100-1 transmits, together with the instruction forrequesting the D2D communication, the information indicating theparameter that characterizes the property of the D2D data transmitted byeach of the anchor UE 100-1 and the UE 100-2, and the informationindicating the data amount of the D2D data of the anchor UE 100-1 andthe UE 100-2, to the eNB 200.

Steps 403 and 404 correspond to steps 203 and 204 in the firstembodiment.

Step 405 corresponds to step 205 in the first embodiment. However, onlythe anchor UE 100-1 receives the information indicating that the D2Dcommunication is permitted, from the eNB 200.

Step 406 corresponds to step 206 in the first embodiment.

(Schematic Operation of Mobile Communication System According to ThirdModification of Embodiment)

Next, by using FIG. 14, a schematic operation of a mobile communicationsystem according to a third modification of the embodiment will bedescribed. FIG. 14 is a sequence diagram showing an operation example ofthe mobile communication system according to the third modification ofthe embodiment. It is noted that description will be provided whilefocusing a portion different from the embodiment and each modificationdescribed above, and description of a similar portion will be omitted,where necessary.

The present modification differs from the above-described firstmodification in that there is an anchor UE100-1.

Step 501 corresponds to step 301 in the first modification.

Step 502 corresponds to step 302 in the first modification. However,only the anchor UE 100-1 transmits the instruction for requesting theD2D communication to the eNB 200.

The UE 100-2 transmits in advance information indicating the parameterthat characterizes the property of the D2D data transmitted by the UE100-2, to the anchor UE 100-1.

The anchor UE 100-1 transmits, together with the instruction forrequesting the D2D communication, the information indicating theparameter that characterizes the property of the D2D data transmitted byeach of the anchor UE 100-1 and the UE 100-2, to the eNB 200.

Steps 503 and 504 correspond to steps 303 and 304 in the firstmodification.

Step 505 corresponds to step 305 in the first modification. However,only the anchor UE 100-1 receives the information indicating that theD2D communication is permitted, from the eNB 200.

Step 506 corresponds to step 306 in the first modification. However,only the anchor UE 100-1 transmits to the eNB 200 the informationindicating the data amount of the D2D data of the anchor UE 100-1 andthe UE 100-2.

It is noted that the UE 100-2 transmits in advance the informationindicating the data amount of the D2D data, to the anchor UE 100-1.

Step 507 corresponds to step 307 in the first modification. However,only the anchor UE 100-1 receives from the eNB 200 the informationindicating the assignment of the D2D communication-use radio resource(bandwidth assignment).

Step 508 corresponds to step 308 in the first modification ofembodiment.

Conclusion of Embodiment

In the present embodiment, the UE 100 (controller) establishes the D2Ddata-use bearer in accordance with the parameter characterizing theproperty of the D2D data. The radio resource assigned in accordance withthe parameter is used to thereby transmit the D2D data corresponding tothe parameter via the D2D data-use bearer according to the parameter. Asa result, the D2D communication-use radio resource is assigned inaccordance with the parameter, and thus, when more radio resources areassigned to the UE 100 having the D2D data of the parameter having ahigh priority, the UE 100 having the D2D data to be preferentiallytransmitted is capable of preferentially transmitting the D2D data to bepreferentially transmitted.

Further, in the present embodiment, when the UE 100 has respectiveparameters of a plurality of pieces of D2D data transmitted by the D2Dcommunication differing from one another, a plurality of pieces of D2Ddata-use bearers are established to the UE 100 in accordance with theparameters of the plurality of pieces of D2D data. As a result, evenwhen the UE 100 has a plurality of pieces of D2D data to be transmittedin the D2D communication, a D2D transmission-use bearer according to therespective parameters are established, and thus, when the radioresources assigned according to the respective parameters, it ispossible to preferentially transmit the D2D data to be preferentiallytransmitted.

Further, in the present embodiment, the UE 100 (controller) furtherestablishes a D2D control bearer used for controlling the D2Dcommunication. The UE 100 performs control of transmitting and/orreceiving, via the D2D control bearer, the keep-alive information forconfirming that the D2D communication connection between the UEs 100 iseffective. As a result, the UE 100 is capable of determining whether theD2D communication connection is effective.

Further, in the present embodiment, the UE 100 (controller) changes thedisplay of the user interface 120 of the UE 100 when not receiving thekeep-alive information for a predetermined period. As a result, whenvisually confirming the display of the user interface 120, a user of theUE 100 is capable of easily recognizing that the keep-alive informationfor confirming that the D2D communication connection is effective is notreceived.

Further, in the present embodiment, the parameter is at least one of theidentifier of the QoS class, the priority, the permitted delay time, andthe permitted packet loss rate. As a result, it is possible to determinethe D2D data to be preferentially transmitted.

Further, in the present embodiment, the UE 100 (controller) establishes,co-existing with the D2D transmission-use bearer, the radio bearer. TheUE 100 (radio transceiver 110) receives, via the radio bearer, theinformation indicating a radio resource assigned by the eNB 200 inaccordance with the parameter.

Other Embodiments

As described above, the present invention has been described with theembodiments. However, it should not be understood that thosedescriptions and drawings constituting a part of this disclosure limitthe present invention. From this disclosure, a variety of alternateembodiments, examples, and applicable techniques will become apparent toone skilled in the art.

For example, in the above-described embodiment, the eNB 200 controls theD2D communication; however, the eNB 200 may not need to control the D2Dcommunication. In this case, when the UE 100-1 and the UE 100-2 are notconnected to the eNB 200, either one of the UE 100-1 or the UE 100-2performs the scheduling for assigning the radio resource for the D2Dcommunication. Here, description proceeds with an assumption that the UE100-1 performs the scheduling.

The UE 100-1 receives the parameter that characterizes the property ofthe D2D data transmitted by the UE 100-2, from the UE 100-2. The UE100-1 assigns the radio resource used by the UE 100-1 and the UE 100-2to transmit the D2D data in accordance with the parameter thatcharacterizes the property of the D2D data transmitted by each of the UE100-1 and the UE 100-2.

It is noted that when not knowing the parameter that characterizes theproperty of the D2D data, the UE 100-1 and the UE 100-2 may inquire thenetwork. When each of the UE 100-1 and the UE 100-2 is not connectedwith the eNB 200 (that is, in the idle state), the parameter may bedetermined on the basis of at least one of past information related withthe D2D data and an application used for the D2D communication.Specifically, when new D2D data transmitted by using the D2Dcommunication is the same or the same in classification as the D2D datatransmitted in the past, the UE 100 determines a parameter thatcharacterizes the property of the D2D data transmitted in the past, as anew parameter that characterizes the property of the D2D datatransmitted by using the D2D communication.

Further, for example, when the application used for the D2Dcommunication requires a real-time performance, the UE 100 determines aparameter that characterizes the property of the D2D data transmitted bythe application, as a parameter having a high priority, and when theapplication used for the D2D communication is a normal data transfer,the UE 100 determines a parameter that characterizes the property of theD2D data transmitted by the application, as a parameter having a lowpriority. Thus, the UE 100 may determine, in accordance with the typesof application used for the D2D communication, the parameter thatcharacterizes the property of the D2D data transmitted by using the D2Dcommunication. As a result, even when the UE 100 is not connected to theeNB 200, it is possible to determine the parameter that characterizesthe property of the D2D data, and the UE 100 is capable of assigning theradio resource in accordance with the parameter.

Further, in the above-described embodiment, the broadcast informationmay be notified to the UE 100 by an AS (Access Stratum) message or maybe notified to the UE 100 by an NAS (Non-Access Stratum) message.

Further, in the above-described embodiment, the UE 100 transmits and/orreceives, via the D2D control bearer, the keep-alive information inorder to confirm the effectiveness of the D2D communication connectionbetween the UEs 100; however, this is not limiting. For example, the UE100 may transmit and/or receive a D2D communication-use reference signalwithout establishing the D2D control-use bearer. The UE 100 determinesthat the D2D communication connection is effective by receiving thereference signal from the partner terminal of the D2D communication. Itis noted that the UE 100 may transmit and receive the D2Dcommunication-use reference signal after establishing the D2Dcontrol-use bearer to thereby determine whether or not the D2Dcommunication connection is effective, and perform other control on theD2D communication via the D2D control-use bearer.

Further, in the above-described embodiment, the radio bearer establishedbetween the UE 100 and the eNB 200 and the D2D-use bearer establishedbetween the UEs 100 may be mapped to the same physical channel, and maybe mapped to a different physical channel.

In addition, the entire content of Japanese Patent Application No.2013-135607 (filed on Jun. 27, 2013) is incorporated in the presentspecification by reference.

INDUSTRIAL APPLICABILITY

Based on the user terminal, processor, and base station according to thepresent invention, it is possible to preferentially transmit the D2Ddata to be preferentially transmitted.

1. A user terminal in a mobile communication system supporting D2D communication that is direct device-to-device communication, comprising: a controller configured to establish a D2D communication bearer used for the D2D communication between the user terminal and other user terminal that is a partner terminal of the D2D communication, in accordance with a parameter that characterizes a property of D2D data transmitted by the D2D communication; and a transmitter configured to transmit the D2D data corresponding to the parameter via the D2D communication bearer depending on the parameter by using a radio resource assigned in accordance with the parameter.
 2. The user terminal according to claim 1, wherein when each of parameters of a plurality of pieces of D2D data transmitted by the D2D communication differs from one another, the controller establishes a plurality of D2D communication bearers in accordance with the parameters respectively corresponding to the plurality of pieces of D2D data.
 3. The user terminal according to claim 1, wherein the controller further establishes a D2D control bearer used for controlling the D2D communication, and the controller performs control of transmitting and/or receiving, via the D2D control bearer, keep-alive information for confirming that a connection between the user terminal and the other user terminal is effective.
 4. The user terminal according to claim 3, wherein the controller changes a display of a user interface of the user terminal when not receiving the keep-alive information for a predetermined period.
 5. The user terminal according to claim 1, wherein the parameter is at least one of an identifier of a QoS class, a priority, a permitted delay time, and a permitted packet loss rate.
 6. The user terminal according to claim 1, wherein the controller establishes, between a base station to which the user terminal is connectable and the user terminal, a radio bearer used for cellular communication that is communication via the base station, co-existing with the D2D communication bearer, and the controller further includes a receiver configured to receive, via the radio bearer, information indicating the radio resource assigned by the base station in accordance with the parameter.
 7. The user terminal according to claim 1, wherein when the user terminal is not connected with a base station, the controller determines the parameter on the basis of at least one of past information related with the D2D data and an application used for the D2D communication.
 8. A processor provided in a user terminal in a mobile communication system supporting D2D communication that is direct device-to-device communication, wherein the processor executes the processes of: establishing a D2D communication bearer used for the direct D2D communication between the user terminal and other user terminal that is a partner terminal of the D2D communication, in accordance with a parameter that characterizes a property of D2D data transmitted by the D2D communication; and transmitting the D2D data corresponding to the parameter via the D2D communication bearer depending on the parameter by using a radio resource assigned in accordance with the parameter.
 9. A base station in a mobile communication system supporting D2D communication that is direct device-to-device communication, comprising: a controller configured to establish a radio bearer used for cellular communication that is communication via the base station, between the base station and a user terminal configured to perform the D2D communication; and a transmitter configured to transmit a radio resource used for the D2D communication, to the user terminal via the radio bearer, wherein the controller assigns the radio resource to the user terminal in accordance with a parameter that characterizes a property of D2D data transmitted by the D2D communication. 